This disclosure is directed to a device to protect male pipe threads during shipment or handling; the thread protector is installed on the exposed threads of pipe in an assembled pipe system to protect from corrosion above ground, under ground or under water. As an example, the thread protector is particularly advantageous for use with small diameter pipe, but not limited to 1/8" to about 6" having tapered threads known as dry seal threads. This pipe is most often galvanized at the mill and shipped in 20 foot lengths to a distributor or end user for cutting to length. Threads will be added to conform to system requirements. When a thread is machined on the pipe, the protective coating (e.g., galvanizing) is removed thus exposing unprotected metal. Cutting and threading removes the protective coating and thereafter leaves an unprotected male thread.
Pipe thread protectors installed at the pipe mill may include shipping wrappers such as paper or tape covers. Also, disposable end caps are known. In very general terms, the variety is unlimited but protection of the pipe (both before and after installation) is irregular, and especially so around the male threads on the pipe. It is fairly common to use metal pipe which has been coated with a thin film (usually galvanizing) to prevent corrosion. In actuality, it does not really prevent corrosion, rather, it merely delays the onset of corrosion. Where the coating is absent, the corrosion starts even more rapidly. The rate of pipe thread corrosion is dependent on environmental conditions. The measure of corrosive severity increased markedly in humid areas, areas near water and especially areas near the sea coast. For instance, a breeze from a salt water body will cause significantly accelerated corrosion of pipe. It is also true at locations which are exposed to widely fluctuating temperature extremes. These and other variables cause wide variation in threaded pipe longevity. As one example, consider a typical one-family residence which has a conventional threaded pipe connection from the gas main to the gas meter. The exposure variations and risk of damage can be quite severe for the gas meter connections. The gas meter is typically installed out of doors and is exposed to inclement weather. Highly corrosive fertilizers, insecticides, etc. accelerate corrosion. Adding the variables mentioned above, exposed connections may corrode and require replacement in quick order when it is intended to least many years. While the failure date is difficult to predict, but in any event, the threaded connections on the meter must be inspected often and corrosion must be dealt with in all circumstances to improve safety and reduce loss of unmetered gas. Failure of the threaded pipe connections is an expensive repair or replacement job; if the threaded connection life can be extended, then safety is increased and cost is reduced.
Several devices have been used in the past. For instance, Teflon tape (a registered trademark of the DuPont Company) is often applied to the threads, also, shrink sleeves aer known. Various weights of grease, adhesives, sealants or bituminous coatings can also be applied to the threads. They provide some measure of protection. In some instances, the previous devices are detrimental in that they trap fluid condensate or otherwise allow capillary migration of fluid directly to the threaded area. Such flow may be miniscule but it will nevertheless contribute to the damage of threads, perhaps in a fashion unseenby visual inspection. One prior art device is an added threaded sleeve such as that shown in the patent of Schmaus, U.S. Pat. No. 2,101,514. This patent is representative of other pipe thread protectors including U.S. Pat. No. 1,168,196. Primarily, the Schmaus structure suffers from limitations arising out of a dissimilar metal junction which gives rise to currents between the metals which may cause corrosion in the presence of an electrolyte. Moreover, Schmaus does not deal with full thread protection. The last thread on the threaded male pipe is viewed as most subject to failure in a threaded pipe system. With normal installation, mechanical loading acts on the region of the last thread, the most vulnerable part of the pipe. Even though the pipe is galvanized, this will not retard corrosion in exposed last thread region. Again, corrosion may be accelerated depending on the nature of environmental conditions. For all these reasons, the improved device of this disclosure provides protection and is therefore markedly more desirable than the devices of the prior art.
This new, useful and unobvious apparatus is a thread protector which functions as a sleeve or cap which fits over the threads at the time of manufacture. When the pipe is threaded, this device can be installed over the threads. The device length covers the threads in most instances. It has a transverse head or covering which forms a sacrificial disc which is easily punched out of the device covering the open end of the pipe prevents foreign matter entering into the pipe. At the time the threaded pipe is installed, the disc can be cleared to leave a sleeve with a surrounding radial shoulder to provide a structurally substantial member for abutting pipe couplings threaded on the pipe. So to speak, the sleeve is forced up the pipe by the coupling to position the sleeve portion sufficiently along the pipe so that all the threads beyond the coupling are protected. The device abuts against the coupling (female fitting) to cover the threads not within the coupling. A dissimilar metal junction between the protective device and pipe or coupling is avoided because the preferred material of this apparatus is a polymer as will be described below. Moreover, sealing against the atmosphere can be easily achieved by packing with a grease, silicon or other sealant. Capillary liquid flow is prevented around the threaded area and coupling face. The present apparatus thus converts readily from a capped thread protector into a sleeve which covers all the exposed threads and thereby prevents corrosion at the exposed threads.